Herceptin and Tykerb News from San Antonio

Lapatinib combined with Trastuzumab worked more effectively than Lapatinib alone for women with HER2 positive advanced breast cancer that progressed on Trastuzumab, according to results released at the 2009 San Antonio Breast Cancer Symposium.

The updated survival analysis was presented by Kimberly Blackwell, MD, associate professor of medicine and director of the clinical trials program in breast cancer at Duke University Medical Center.

Study Background

HER2 positive breast cancers have too many copies of the HER2 gene. The extra copies of the HER2 gene in the nucleus of the cell produce excess HER2 protein, causing cancer cells to grow and multiply. In women with metastatic breast cancer, the cancer cells have traveled to other organs such as the bones, liver, lungs or brain.

Lapatinib (brand name: Tykerb), a pill, is a type of targeted therapy called a Tyrosine Kinase Inhibitor. This medicine targets human epidermal growth factor receptor 2 (HER2) as well as epidermal growth factor receptor 1 (EGFR, also known as HER1).

Trastuzumab (brand name: Herceptin), another targeted therapy, is a monoclonal antibody that works by attaching to and blocking the HER2 receptors on cancer cells, thereby slowing breast cancer growth.

Study Design and Results

This Phase III study included 296 women with HER2 positive metastatic breast cancer that had progressed after an average of three prior treatments containing Trastuzumab. The women were randomly divided into two groups. The first group received lapatinib once daily, and the second group received Lapatinib in combination with Trastuzumab. Among the women taking Lapatinib alone, 52 percent had disease progression after four or more weeks and switched to the combination therapy.

Median progression-free survival, or time from the beginning of treatment until the cancer grew, was 12 weeks in the combination group and 8.1 weeks in the group taking Lapatinib alone. Median overall survival, or time before death from any cause including breast cancer, was 60.7 weeks for women taking the combination treatment compared to 41.4 for Lapatinib alone. This number represents a 25 percent reduction in the risk of death for women taking the combination treatment.

The researchers concluded that two targeted therapies given together are more effective than Lapatinib alone. The survival benefit of the combination therapy may be underestimated in the study due to the large number of women who crossed over to the combination arm from the Lapatinib only arm.

What Does This Study Mean for Me?

If you are in treatment for HER2 positive metastatic breast cancer that has progressed on Trastuzumab alone, talk to your doctor to determine if taking this treatment makes sense for you. "These two targeted therapies against HER2, sort of a ‘one-two punch,’ conveyed a more than four month significant improvement in survival when compared to Lapatinib alone," LBBC Medical Advisory Board member Dr. Blackwell said during a December 11 press conference at the Symposium. "This represents a step forward toward a day when we don’t have to give chemotherapy for breast cancer at all."